The present invention relates generally to a medical instrument for use in performing phacoemulsification or extracapsular cataract surgery, and a method for utilizing the medical instrument in performing such surgery. More particularly, the invention relates to a medical instrument for use in performing an anterior and/or posterior capsulotomy during phacoemulsification or extracapsular cataract surgery.
The medical instrument in accordance with the present invention includes a retractable-extendible wire cautery portion extendible to correspond to a desired peripheral extent of a portion of the capsule to be removed.
In performing a capsulotomy during cataract surgery by phacoemulsification, a small incision is made in the cornea through which the cautery portion is inserted while retracted to render it as small as possible. Thereafter, the cautery portion is extended and positioned in contact with the anterior (or posterior) lens capsule, so as to sear the periphery of a portion of the lens capsule to be removed. Thereafter, the entire periphery of the lens capsule portion to be removed is seared in a consistently perfect manner.
The human eye includes a lens having the configuration of a biconvex disc. The lens surface comprises a capsule which includes an anterior capsule and a posterior capsule which meet at an equator. Zonules extending from the ciliary body are attached to the lens equator so as to secure the lens in position. Disposed within the lens capsule is a softer cortex and a firm inner nucleus.
In a healthy human eye, the lens is formed of a clear crystalline protein, however, the lens will at times opacify to form what is known as a cataract.
Up to about five years ago, the preferred method employed to remove the cataract was the (manual) extracapsular technique. In such procedure, the eye is opened at the superior limbus, and either a bent needle (or any other curved sharp edged instrument) or special forceps are employed to open the anterior lens capsule and express from within the capsule the nucleus of the lens. Thereafter, the remaining cortical material is removed so as to thus leave a clear posterior lens capsule in the eye, which capsule provides a barrier between the anterior chamber and the vitreous cavity of the eye, as well as a resting surface for an implanted artificial lens.
In recent years phacoemulsification has become the procedure of choice for cataract extraction. In this procedure a small incision in either scleral or corneal region is made (with intracorneal portion--the "tunnel"). Through this incision an anterior opening in the lens capsule is performed. A probe containing an ultrasonic wave generator, a rinsing fluid inflow end and a suction tip is inserted into the capsular bag. Dense compacted proteins of lens nucleus are broken by ultrasonic power and are emulsified in rinsing fluid. Emulsified nuclear proteins as well as soft peripheral lens proteins ("cortex") are removed from the eye by the suction unit.
The main advantage of the phacoemulsification technique over the manual extracapsular technique is the small surgical wound needed to perform it. In manual extracapsular technique the nucleus of the lens is expressed from the eye as a whole. For this reason the surgical wound, in order to allow for the nucleus to be expressed, has to be about 7 millimeters wide.
As in phacoemulsification technique the nucleus is emulsified, it is no longer necessary for the surgical wound to be as wide, and 2-3 millimeters are sufficient.
A smaller wound is beneficial in regard to rate of visual rehabilitation after operation as well as post-surgical astigmatism prevalence and severity.
In performing cataract extraction by phacoemulsification two mandatory demands have to be met. First, surgical tools used for intraocular manipulations during surgery should be small enough in order to account for their insertion through the small surgical wound (2-3 millimeters in biggest dimension). Second, edges of the capsulotomy should be smooth and uniform. In contrast to extracapsular manual technique, in which non-homogenous edges of the capsulotomy were acceptable and allowed for different non-continuous capsular opening techniques (capsular puncture of interrupted cutting, later connected radially), in phacoemulsification non-uniform edges of capsulatory are unacceptable. The reason for this demand is that during phacoemulsification process the presence of an anterior capsular strands may result in capsular tear extending into the posterior capsule due to strands being captured and pulled by the suction unit. A tear in the posterior capsule prevents the posterior lens implantation in most cases and might result in vitreous loss.
At present opening of the anterior capsule during phacoemulsification is made by capsulophexis, whereby the surgeon opens a centrifugal linear opening in the capsule and then grips the anterior capsule edge with special forceps and creates a continuous circular tear of the anterior capsule.
Correctly performed, this maneuver results in a uniform smooth edge capsular opening yet expressing this technique demands high degree of surgical skill and if the surgeon loses dull control on tearing procedure, the tear might be directed posteriority and cause opening in posterior capsule with all its above mentioned complications.
Performance of a posterior capsulotomy wherein the posterior capsule remaining in the eye is itself incised is selective, depending upon the particular surgeon's preference. Such a technique may be employed to avoid the possibility of later opacification of the posterior capsule by performing the posterior capsulotomy in the final stages of the cataract extraction procedure, such as after an intraocular lens has been implanted.
Accordingly, and in view of the ever-increasing incidence of cataracts, there has developed a desideratum for a surgical instrument and technique for performing an anterior (or posterior) capsulotomy during phacoemulsification or extracapsular cataract surgery which overcomes the shortcomings and risks encountered using current instruments and techniques.
Some of the various attempts which have been made in the general field of cautery-type or heated-type medical instruments include: the "DENTAL INSTRUMENT" disclosed in U.S. Pat. No. 1,335,987 issued in 1920 to Reid et al; the "THERAPEUTIC APPLIANCE" disclosed in U.S. Pat. No. 1,615,828 issued in 1927 to Chesney; the "MEANS FOR EFFECTING THE BLOODLESS REMOVAL OF DISEASED TISSUE" disclosed in U.S. Pat. No. 1,919,543 issued in 1933 to Doane; the "METHOD OF AND APPARATUS FOR THE INTRACAPSULAR EXTRACTION OF THE CRYSTALLINE LENS OF AN EYE" disclosed in U.S. Pat. No. 2,033,397 issued in 1936 to Richman; the APPARATUS FOR INTRAOCULAR SURGERY" disclosed in U.S. Pat. No. 3,884,237 issued in 1975 to O'Malley et al; the "CAUTERY DEVICE FOR OPHTHALMIC OR THE LIKE SURGICAL APPLICATION" disclosed in U.S. Pat. No. 4,108,181 issued in 1978 to Saliaris; the "DEVICE FOR REMOVING EXCRESCENCES AND POLYPS" disclosed in U.S. Pat. No. 4,202,338 issued in 1980 to Bitrolf; the "EXPERIMENTAL INTRAOCULAR COAGULATION" disclosed in article by Peyman et al appearing in Opthalmic Surgery, January-February 1972, Volume 3, No. 1, pp. 32-37; and the "BIOPSY IN PROCTOLOGY" disclosed in an article by Gorsch appearing in American Journal of Surgery, June 1936, p. 484.
However, none of such known medical instruments and/or techniques provide any means for performing a consistently perfect capsulotomy during extracapsular cataract surgery.
U.S. Pat. No. 4,481,948 to Sole, entitled "MEDICAL INSTRUMENT, AND METHODS OF CONSTRUCTING AND UTILIZING SAME", which is incorporated by reference as if fully set forth herein, discloses a medical instrument including a cautery portion for use in performing an anterior or posterior capsulotomy during extracapsular cataract extraction surgery. A substantially rigid stem portion is connected between the cautery portion and a handle portion, and is provided with bends to facilitate maneuverability of the cautery portion and to avoid substantial interference with the surgical field of vision by the handle portion. An electrical path is defined through the handle portion and stem portion to the cautery portion so as to permit electrical current to be supplied to the cautery portion from an electrical apparatus which generates a radio frequency current. The cautery portion, as supplied with radio frequency current, becomes heated when in contact with an eye lens capsule so as to instantaneously and uniformly sear a peripheral extent of a portion of the lens capsule to be removed during surgery.
However, the medical instrument invented by Sole suffers limitations. First, having a wire cautery portion of a permanent size, it requires a large incision to be performed in the superior limbus in order to insert the wire in close proximity with the capsule, which incision should be wider than the diameter of the cautery portion employed, i.e., in the range of 7-10 millimeters. Second, although only one face of the cautery portion is effectively used to sear the periphery of a portion of an anterior (and/or posterior) capsule to be removed, the other face thereof heats as well, which may cause damage to neighboring eye tissue, such as the internal face of the cornea. Third, the cautery wire is rigid and is set at a constant diameter--a fact that does not allow for intraoperative diameter adjustment in accordance with relevant surgical factors like lens dimensions, puppilary dilation, etc.
There is thus a widely recognized need for, and it would be highly advantageous to have, a medical instrument devoid of the above limitation.
These limitations are avoided by the medical instrument of the present invention by providing a retractable-extendible cautery portion designed to have only one face thereof heated.